1. Field of the Invention
The present invention relates to an image display device such as a projector for displaying an image on a projection surface such as a screen.
2. Description of the Related Art
The image display device such as a projector is provided for projecting an image such as a still image or an animated image of an OHP or a slide on a projection surface such as a screen.
Recently, in making the presentation to a plurality of people concerned, a document stored in a computer device is projected on an image display device, and the explanation or the like is made using an image displayed on the projection surface (see JP-A-2003-280091 (patent document 1), for example).
In displaying an image on the projection surface using such an image display device, when unevenness exists on the projection surface or an obstacle exists on the projection surface or in the midst of an optical path of a projection light, there arises a drawback that a projected image is distorted or a shadow of the obstacle is displayed on the projection surface. Accordingly, several methods have been proposed conventionally for preventing the occurrence of such drawback.
For example, there has been known one conventional image display device which detects whether or not a projection light is projected in the oblique direction relative to a screen. When the projecting direction is oblique relative to the screen, a trapezoidal distortion generated due to the presence of the oblique projecting direction is automatically corrected (see JP-A-4-355740 (patent document 2), for example).
Further, there has been also known an image display device which radiates detection waves such as infrared rays to a screen, and detects reflection waves reflected from a screen side thus detecting the presence or non-presence of an obstacle. Then, when the obstacle is detected, a quantity of projection light is reduced or the projection is interrupted by taking a case that the obstacle is a human into consideration (see JP-A-2004-70298 (patent document 3), for example).